The effect of spatial and temporal correlations between specific image elements which determine the detectability of small changes in radiopacity in tissue of diagnostic interest are being evaluated in vitro using computer simulations and quantitative measurements derived from radiographic phantoms. This work compliments collaborative research done in association with extramural programs staff and the Restorative materials Program Branch, and the National Bureau of Standards to develop a prototype x-ray system which permits accurate reproduction of exposure geometry from one examination to the next. The system will contain a quantum-efficient, non-film, intraoral detector coupled with some sort of scanning x-ray source which produces computer-processed digital images in near real time. Other studies consider the applicability of information theory to the description of diagnostic performance obtainable from radiographic systems, and the use of computerized tomosynthesis to describe dental structures using limited-angle projection geometry.